Type IV pili are essential virulence factors for many Gram-negative bacterial pathogens and type IV pilin proteins have made effective vaccines for veterinary use. Burkholderia mallei and B. psuedomallei, the causative agents of glanders and melioidosis, respectively, represent significant biowarfare/bioterrorism threats. A search of the unfinished genomes of these microorganisms reveals that they contain identical genes for type IV pilin proteins. We plan to conduct pilot studies that will provide preliminary data for future studies of the use of the type IV pilin proteins of these organisms as vaccines. Our first specific aim is to purify soluble pilin protein, raise antisera, and test sera from animals sacrificed at various time periods after experimental glanders infection for antibody responses to pilin. Our second aim is to construct a strain of B. mallei that has a deletion in the pilin gene and test its ability to express pilin, pili and associated phenotypes in vitro. The data and reagents generated in these studies will be used for future studies to assess the role of the type IV pilus in experimental glanders infection and the protective efficacy of passive and active pilin immunization against glanders and melioidosis. [unreadable] [unreadable]